IMMUNITY Flashcards
what is the immune system?
a mechanism that defends an organism against pathogens
immune:
the ability of the body to resist pathogens
what is an antigen?
a substance that is foreign to the body and stimulates an immune response
made of proteins, glycoproteins, carbs and glycolipids
all cells in your body have antigens on the cell membrane that act as a marker for cell recognition
antigens on the cells in your body are recognized as self-antigens
antigens on the foreign cells entering your body are recognized as non-self-antigens, which stimulates an immune response where white blood cells recognize the foreign cell as a pathogen and destroys it
what is the immune response?
the body’s immune system responding to non-self antigens involving the production of antibodies and killing of pathogens and cells infected
what are the external defenses in our body?
ciliated epithelial cells sweep mucus in airways preventing pathogens
hydrochloric acid in the stomach destroy ingested pathogens
blood platelets make blood clot to prevent pathogens entering
skin prevents colonization of bacteria and pathogens
what is the process of phagocytosis?
when a body is invaded by a pathogen, cells release a chemical called Histamine which attracts neutrophils to collect at the infection site
the pathogen in marked by antibodies and neutrophils recognize the mark on the pathogen and engulf the pathogen by phagocytosis
the pathogen is now called a phagosome
the neutrophil’s lysosomes fuse with the phagosome and destroy the pathogen
dead neutrophils collect at the infection site as pus
what are the 2 types of phagocytes?
macrophages and neutrophils
what are 2 types of lymphocytes?
B-lymphocytes and T-lymphocytes
what is the role of B-lymphocytes in humoral immune response?
when pathogens enter the body for the first time some of them are destroyed by macrophages that expose the pathogens antigens on its surface
T helper cells with receptors that fit the antigen will release cytokine which will stimulate B cells to replicate and divide by mitosis
some of these cells B cells are plasma cells that produce antibodies quickly and secrete them in the blood
plasma cells are short-lived but their antibodies stay in the blood longer
the antibodies coat and mark the antigen on the surface of the pathogens for phagocytosis
other B cells become memory cells which remain circulating in the body for a long time, maybe even a lifetime
what is immunological memory?
the ability of the immune system to respond quickly to antigens that it recognizes as it has entered the body before
what is the primary immune response?
when B-lymphocytes meet the antigen of the pathogen for the first time
it tales a few days for enough B cells to be produced to make enough antibodies
during this time, the pathogen may have formed a large population to make you ill
primary immune response is slow
what is the secondary immune response?
when the same antigen is reintroduced after the first infection, the memory cells in the body rapidly divide and develop plasma and memory cells
plasma cells produce a large amount of antibodies so that the pathogen can be destroyed and removed before any symptoms develop
what are antibodies?
globular glycoproteins made up of 4 polypeptides, two heavy and two light, held by disulphide bonds
what are the two regions of an antibody?
variable region and constant region
what is the variable region?
formed of both heavy and light polypeptide chains
there is a different chain for every antibody
the sequence of the antibody in the variable region give it a specific 3D shape that form 2 identical antigen bonding sites
the hinge region gives the antibody flexibility to bind around the antigen
what is the constant region?
formed of heavy chains only
it is the same in all antibodies
how do antibodies attack?
some antibodies bind with antigens on the surface of a pathogen to mark them for them to be destroyed by phagocytosis
some antibodies are antitoxins which combine with toxins released by the pathogen and neutralize them making them harmless
what is a T-lymphocyte?
is produced in the bone marrow and matures in thymus gland
each mature T cell has a receptor that is complementary to antigens of pathogens
what is the role of T-lymphocytes in cellular immune response?
T cells are activated when they encounter its specific antigen on a host cell such as a macrophage that has engulfed a pathogen and is exposing its antigens on its surface (done by T helper cell)
the activated T cells respond to the antigen by dividing to form clones that develop T killer cells
what does a T helper cell do?
these release a hormone called cytokine that stimulates:
T killer and B cells to divide
causes macrophages to carry out phagocytosis more vigorously
what does a T killer cell do?
they search the body for invaded cells that’re displaying foreign antigens on their surface from the pathogens
then the T killer cells recognize the antigens, they attach themselves to the surface of the infected cell and secrete toxins that will cause water and ions to diffuse into the cell making it lysed and making it burst
what are the two types of immunity?
passive and active
what is active immunity?
long tern immunity gained when a foreign antigen enters the body, immune response occurs, antibodies are produced by plasma cells and memory cells are produced
what is natural active immunity?
when the body has made its own antibodies as a result of an infection
what is artificial active immunity?
antibodies are produced against antigens of a vaccine
what is passive immunity?
immediate but temporary immunity gained without an immune response
what is natural passive immunity?
mother to child across placenta or breastfeeding
what is artificial passive immunity?
antibody transfer
what is a vaccine?
a vaccine stimulates a primary immune response and produces antibodies and memory cells
they don’t cause illness as they contain either:
inactivated form of a pathogen
less violent form of a pathogen
isolated antigens from a pathogen
what are the problems with a vaccine?
poor response:
a body might not have enough proteins to stimulate an immune response and form antibodies. this could cause the body to actually develop the disease and can be transmitted. this can be prevented by herd immunity as everyone is immune and can’t transmit the disease even if one person has a poor response
antigenic variation:
- antigenic drift:
when a minor change occurs in the shape of the viral antigen, still causing memory cells to recognize them and activate a secondary immune response - antigenic shift:
when a major change occurs in the shape of the viral antigen causing memory cells to not recognize it and any previous vaccine given for a previous strain will be ineffective
antigenic concealment:
some pathogens hide and live inside cells to be protected from antibodies
what is herd immunity?
when a high enough proportion of the population is vaccinated against a disease, that any one infected person will have a lower opportunity to infect other people as the others will have taken a vaccine and has immunity and memory cells
how could WHO eradicate smallpox?
smallpox is a highly infectious disease that produced red spots filled with pus all over the body caused by the variola virus and was transmitted through direct contact
variola virus is stable and doesn’t mutate or have antigenic variation which means that the same vaccine can be used worldwide
the virus didn’t infect animals which makes it easier to break the transmission cycle
the vaccine was freeze-dried and could be kept in high temperatures for 6 months which made it suitable to be transported worldwide
the virus was easy to administer as they used reusable needles that push the vaccine into the skin
infected people were easy to identify
why did WHO fail to eradicate measles?
measles is a highly infectious disease caused by a microbilli virus that is spread by airborne droplets
WHO failed at eradicating measles because of:
poor response to the vaccine from children who suffer from malnutrition
difficult to give boosters due to a shifting population
migrants and refugees can spread the disease
more neutrophils =
more lymphocytes =
more neutrophils = bacterial infection
more lymphocytes = viral infection
what is leukemia?
a cancer of the bone marrow stem cells in which they divide uncontrollably forming a large amount of immature WBC’s flowing into the bloodstream
what are the types of leukemia?
myliod leukemia: cancer of myliod stem cells that produce neutrophils
lymphoblastic leukemia: cancer of lymphoid stem cells that produce lymphocytes
acute leukemia: develops quickly, has severe effects and has to be treated immediately
chronic leukemia: takes many years to develop and treatment is given when the disease is most likely to be cured
what is the effect of leukemia on health?
the rapid production of immature WBC’s will cause an imbalance of the normal blood components so there won’t be enough RBC’s and platelets, causing anemia
what is an auto-immune disease?
a disease where there is a mistaken immune response to a self-antigen, leading to the production of antibodies and destruction of self tissues
what is Myasthenia Gravis (MG)
an auto immune disease that targets neuromuscular junctions
the neurons contain vesicles pilled with acetylcholine the acetylcholine is released in the gap and binds with the receptors on the cell membrane of the muscle cell resulting in muscle contraction
people with MG have T-helper cells that are specific for acetylcholine receptors
these T-helper cells recognize the acetylcholine receptors as non-self antigens and stimulate B cells to divide forming plasma cells that secrete antibodies
these antibodies bind to the receptor, blocking the transmission of the impluse causing the muscle to not stimulate and relax, this causes the muscle to weaken
what is the treatment of MG?
a drug that releases acetylcholine estrase enzyme which increases the concentration of acetylcholine so it’s actions lasts longer
what are monoclonal antibodies?
they’re produced by a clone of B cells that are complementary to a specific antigen
B cells don’t divide and don’t live long
this is solved by fusing B cells with myeloma cells{cancerous} forming hybridoma cells
hybridoma cells are cultured and continue to grow and divide, they secrete the specific antibodies that were produced by the original clone of B cells
how are monoclonal antibodies produced?
a mouse is injected with the antigen
an immune response takes place and plasma cells are produced
two or three weeks later, the mouse is killed and it’s spleen is removed
B cells are collected
B cells are fused with myeloma cells forming hybridoma cells
hybridoma cells are separated individually and cultured in a well to divide
antibodies are removed from wells and are tested with relevant antigen
the antibody that binds to the antigen in the correct monoclonal
what are the uses of monoclonal antibodies in diagnosis and in treatment?
in diagnosis:
1-localization the position of blood clots
2-identification of pathogen
3-identification and location of tumors
in treatment:
1-herceptin used in treatment of breast cancer
2-blocking growth of cancer cells
3-treatment of rehumatoid arthritis
how are monoclonal antibodies humanized?
they’re produced by mice, so when they’re introduced to humans they trigger an immune response as they’re recognized as non-self antigens
this was solved by
- altering the genes the polypeptide chains so they code for human sequence
- changing the types and positions pf sugar groups on the antibody
